linux-kernel - Re: [PATCH] i2c: imx: make controller available until system suspend_noirq() and from resume

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Message-ID: <6d6xgvuvu74hm5466xeovgr4qqkwxaxaoeemvfdty3dqnl4gjp@axlzm6mxnzkv>
Date: Thu, 5 Dec 2024 12:53:42 +0100
From: Andi Shyti <andi.shyti@...nel.org>
To: carlos.song@....com
Cc: o.rempel@...gutronix.de, kernel@...gutronix.de, shawnguo@...nel.org, 
	s.hauer@...gutronix.de, festevam@...il.com, frank.li@....com, linux-i2c@...r.kernel.org, 
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: imx: make controller available until system
 suspend_noirq() and from resume_noirq()

Hi Carlos,

...

> +static int i2c_imx_suspend(struct device *dev)
> +{
> +	/*
> +	 * Some I2C devices may need I2C controller up during resume_noirq()
> +	 * or suspend_noirq(), if the controller is autosuspended, there is
> +	 * no way to wakeup it once runtime pm is disabled (in suspend_late()).
> +	 * When system resume, I2C controller will be available until runtime pm
> +	 * is enabled(in_resume_early()). But it is too late for some devices.
> +	 * Wakeup the controller in suspend() callback while runtime pm is enabled,
> +	 * I2C controller will be available until suspend_noirq() callback
> +	 * (pm_runtime_force_suspend()) is called. During the resume, I2C controller
> +	 * can be restored by resume_noirq() callback (pm_runtime_force_resume()).
> +	 * Then resume() callback enables autosuspend. It will make I2C controller
> +	 * available until system suspend_noirq() and from resume_noirq().
> +	 */

Just made some little adjustments to the comment above, please
let me know if they are fine:

	/*
	 * Some I2C devices may need the I2C controller to remain active
	 * during resume_noirq() or suspend_noirq(). If the controller is
	 * autosuspended, there is no way to wake it up once runtime PM is
	 * disabled (in suspend_late()).
	 *
	 * During system resume, the I2C controller will be available only
	 * after runtime PM is re-enabled (in resume_early()). However, this
	 * may be too late for some devices.
	 *
	 * Wake up the controller in the suspend() callback while runtime PM
	 * is still enabled. The I2C controller will remain available until
	 * the suspend_noirq() callback (pm_runtime_force_suspend()) is
	 * called. During resume, the I2C controller can be restored by the
	 * resume_noirq() callback (pm_runtime_force_resume()).
	 *
	 * Finally, the resume() callback re-enables autosuspend, ensuring
	 * the I2C controller remains available until the system enters
	 * suspend_noirq() and from resume_noirq().
	 */

If so, I will take it in.

Andi

> +	return pm_runtime_resume_and_get(dev);
> +}